The Bronx (/brɒŋks/ BRONKS) is the northernmost of the five boroughs of New York City, coextensive with Bronx County, in the U.S. state of New York. The borough shares a land border with Westchester County, New York to its north; to its south and west, the New York City borough of Manhattan lies across the Harlem River; and to its south and east is the borough of Queens, across the East River. The Bronx, the only New York City borough located primarily on the U.S. mainland, has a land area of 42 square miles (109 km) and a population of 1,472,654 at the 2020 census. It has the fourth-largest area, fourth-highest population, and third-highest population density of the boroughs.
The Bronx is divided by the Bronx River into a hillier section in the west, and a flatter eastern section. East and west street names are divided by Jerome Avenue. The West Bronx was annexed to New York City in 1874, and the areas east of the Bronx River in 1895. Bronx County was separated from New York County (modern-day Manhattan) in 1914. About a quarter of the Bronx's area is open space, including Woodlawn Cemetery, Van Cortlandt Park, Pelham Bay Park, the New York Botanical Garden, and the Bronx Zoo in the borough's north and center. The Thain Family Forest at the New York Botanical Garden is thousands of years old and is New York City's largest remaining tract of the original forest that once covered the city. These open spaces are primarily on land reserved in the late 19th century as urban development progressed north and east from Manhattan. The Bronx is also home to Yankee Stadium of Major League Baseball.